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Old     (dru1974)      Join Date: Nov 2009       12-06-2009, 10:11 AM Reply   
Is everyone who rides behind an indmar powered boat using the suggested octane 89n petrol or is it ok to run octane 87......My uncles have boats aswell, one has a mb with a merc power plant and the other rides behind a calabria with a merc i think.....they are running octane 87 fuel. but they have more money than they know what to do with so repairs arent an would think running octane 89 wouldn't be an issue either.

I cant see it being a problem if that is what you run from new.
Old     (razzman)      Join Date: Dec 2006       12-06-2009, 10:56 AM Reply   
Well i run the 89 in my '07 LSV as i've never seen reason to run 87 and imo for the few cents difference i don't see why one would unless in Canada you don't have it. It's like a $4 difference in a tank here. I believe the ecm's are tuned for a specific output based on the 89, dunno. Unless you get advise from an actual marine mechanic everything else is hearsay. Call Indmar and ask them why not or what will happen.

Here's what Indmar says:

All current production engines are designed to operate on 89 octane, unleaded fuel. Little or no performance gain will be realized by using fuel of a higher octane rating than the engine requires. If your engine is a 2007 Model, equipped with ETX-CAT (catalytic converter) exhaust manifolds, the use of any leaded fuel will disable the catalysts, prevent the engine from operating properly and void the warranty on the engine.

The Malibu LS1 and the MasterCraft LQ9 engines require the use of 93-octane fuel. Failure to use 93-octane fuel will result in engine damage that is not covered by your engine warranty.
Old     (dru1974)      Join Date: Nov 2009       12-06-2009, 11:12 AM Reply   
Just curious as we get farm fuel which is the same as regular but coulerd.....not worried much about the cost Razz....Thankyou
Old     (99_slaunch)      Join Date: Oct 2005       12-06-2009, 11:29 AM Reply   
I've run 87 in our 05 supra with no problems. I only did it when it was not weighted. With the extra weight of ballast it may cause it to ping.
Old     (rallyart)      Join Date: Nov 2006       12-06-2009, 11:33 AM Reply   
Marked fuel is still unleaded in Alberta, except for some aviation gas. It's 87 octane usually, for farm fuel. You have lower combustion pressures at 2400 feet in Medicine Hat than at sea level so the octane requirement is slightly lower but not so much lower that you could run 87 instead of 89. If there is a knock sensor and full throttle engine management on your Indmar you could get away with it. Many fuel systems don't manage the engine the same at full throttle.
The Mercruisers only require 87 octane so it's not an issue with them.
Old     (jesse1983)      Join Date: Oct 2008       12-06-2009, 2:41 PM Reply   
I ran a tank of 87 with my Indmar MCX. It was all that was available at the dock that day and it took an entire tank. I didn't have any problems, but have only done it once. 89 doesn't cost that much more, so if it's available...
Old     (05mobiuslsv)      Join Date: Apr 2006       12-06-2009, 3:10 PM Reply   
If you are going to burn the gas that outing 87 is fine. If the gas will be sitting for several days or a week or more go with the 89 octane gas. I read somewhere where Indmar said the same thing but can't remember where that was.
Old     (ajholt7)      Join Date: Apr 2009       12-06-2009, 3:11 PM Reply   
I always run 87 in my MarinePower. No problems.
Old     (craig_f)      Join Date: Feb 2008       12-06-2009, 9:39 PM Reply   
I have had problems running 87 in a 06 supra with the 340 indmar. Knock sensor retarded timing so much it did not want to start when warm.
Old     (05mobiuslsv)      Join Date: Apr 2006       12-06-2009, 9:44 PM Reply   
That has nothing to do with the octane of the gas craig.
Old     (craig_f)      Join Date: Feb 2008       12-06-2009, 9:55 PM Reply   
might have been straight bad gas then, but the 3 times I have put 87 in by necessity has resulted in the same prob. I admit that this was my half-assed non-mechanical diagnostic, but I KNOW it has always ran like crap on low octane gas.
Old     (amo)      Join Date: Jan 2009       12-07-2009, 6:17 AM Reply   
get a boat with a PCM = no more gas problems.
Old     (05mobiuslsv)      Join Date: Apr 2006       12-07-2009, 6:46 AM Reply   
craig it's called heat soak.
Old     (dru1974)      Join Date: Nov 2009       12-07-2009, 7:13 AM Reply   
get a boat with a pcm....dumb statement.....cuz that'll make all the differance rite!!!!!
Ya know I used to be a correct craft guy too, actually had three of them. pcm is still a 350 block dork
Old     (dru1974)      Join Date: Nov 2009       12-07-2009, 7:38 AM Reply   
also i never said i ahve any boat problems
Old     (amo)      Join Date: Jan 2009       12-07-2009, 7:59 AM Reply   
Hey Drew, cool down man. It was meant for Craig. I had a 07 Supra, and mine did the same thing his did. After another bout with one more Indmar boat I decided enough was enough. PCM is a better engine; and not just because it takes 87 without the above mentioned issues. To answer your question, from my experience, you better use 89 or higher in an Indmar. I believe that's what the manual says.
Old     (pnichols)      Join Date: Jan 2007       12-07-2009, 10:46 AM Reply   
I have two buddies that always run 87 octane in their boats both have Indmar engines. I almost always use 89, but have used 87 a couple of times.

Be careful using farm fuel. I know on trucks that are still under the manufacture warranty, if you us farm fuel it will void any warranty work on your engine. The dye in the gas also dyes everything it touches and if they have to take pics to send in to get manufacture approval, your dead in the water.
Old     (wakesetter101)      Join Date: Oct 2005       12-07-2009, 2:39 PM Reply   
I only use 87. Might run 93 through it once a year. My boat cant tell the difference from one to the other.
Old     (cwkoch)      Join Date: Aug 2006       12-08-2009, 7:17 AM Reply   
Run the recommended fuel. It has to do with compression ratio and timing. If it calls for running 89, running 87 will more than likely give you detonation. On a newer engine not a huge deal, the knock sensor should tell the computer to retard the timing, but with that you're losing power. When they spec the fuel you should be running, it's not some magic number they just pulled out of thin air that doesn't matter.
Old     (mcd)      Join Date: Mar 2009       12-08-2009, 11:49 AM Reply   
Most Merc engines are rated for 87. I'd stick with the 89. That's what I run in my PCM.
Old     (rallyart)      Join Date: Nov 2006       12-08-2009, 12:23 PM Reply   
Generally with any engine it is best to stick with the recommended octane numbers. In North America that is by the (R+M)/2 rating. Some specialty fuels only give the Research Octane number and not the Motor Octane number. The R number is usually higher so the R+M rating will be less.
Running a lower octane rating than recommended can lead to pre-ignition and detonation which damages parts and drops power. At high altitude the combustion pressures are less so the need for a high octane is reduced. That's the only time you might feel comfortable running lower octane. If you have forced induction like a turbo, you still want the rated octane.
Running a higher octane than required adds to your expense without benefit and slightly reduces the power your engine produces because it burns too slow.
If you have a sophisticated engine management system it is possible to run lower octane fuel and not damage the engine at a slight loss in power and economy. The economy loss is not as much as the reduced price of the lower octane fuel so you might come out ahead. If some part of the engine management system fails you run the risk of damaging a sophisticated expensive engine.
Old     (cwkoch)      Join Date: Aug 2006       12-08-2009, 12:29 PM Reply   
^^^^^ Well said ^^^^^^
Old     (dru1974)      Join Date: Nov 2009       12-08-2009, 6:17 PM Reply   
it makes sense, but we are 2400 ft above sea level here i wont chance it. Iwonder we had a 92 supra ts6m that was a previouse comp tow boat in the 90s, it used to shut down at full throttle after 5 mins or so. only would do it with no load, meanin not pulling a skier, but when i was bare footing it was never an issue, being only 19 at the time i didn't give a ^%###. Now being the owner of the boat things seem to matter a lil more "funny how that works eh"
Old     (ridealready)      Join Date: Feb 2006       12-10-2009, 7:25 PM Reply   
So I run premium in my 06 Supra. Is that overkill?? I have heard that 89 grade sits for long periods of time at gas stations due to most car owners going premium or 87. Thoughts??? Am I wasting my money?? Indmar 325 MPI
Old     (05mobiuslsv)      Join Date: Apr 2006       12-10-2009, 8:33 PM Reply   
Yes you are waisting your money, but it's not much money if that makes you feel better. Premium unleaded is very clean gas though if that makes you feel better.
Old     (ajholt7)      Join Date: Apr 2009       12-11-2009, 1:42 AM Reply   
Drew isn't the farm fuel with the dye in it Diesel. It is around here.
Old     (chpthril)      Join Date: Oct 2007       12-11-2009, 4:05 AM Reply   
"Premium unleaded is very clean gas though if that makes you feel better."

This is exactly what the oil companies want you to believe. It's incorrect. The Octane rating has ZERO to do with the cleanliness of the fuel, or even how clean it burns. The Octane rating is what percentage of Octane and Heptene the fuel is blended at. Heptane is what gives fuel it's BOOM, in other words, the higher the Heptane molecules (power Octane molecules) the more volatile the fuel is. Volatility is how the fuel reacts to heat. Higher volatility (lower Octane), the less heat it take to combust, the lower the volatility (higher Octane) the more heat it takes to combust.

This is why high Octane fuel is needed in high compression engine, it's to prevent pre-ignition. Compression creates heat, this heat will ignite the air/fuel mixture, so a lower volatility (higher Octane, lower Heptane fuel blend) is needed to resist this heat and not pre-ignite.

The EPA regulates cleaning additives in fuel. EVERY gallon of fuel get the same additives when it's pumped into the pipeline for distribution. Now, at the end, when the oil company pumps out oil to distribute to thier stations, they do add some additional proprietary additives, where as the mom n pop and off-brand stations get the same gas, just with out the "special" crap added.

Trust me, it's smoke and mirrors. Use the Octane level recommended by your manufacturer. I've actually seen fuel problems created by the additives used by one particular major oil company. Bottom line, using an Octane level other then that what is recommended by your manufacturer will not give you any performance benefits or reduce emissions, and in some cases, can lead to engine damage. A gallon of 93 Oct has no more BTU's then a gallon of 87 Oct.

ALL fuel will begin to go stale in about 3 months, the Octane rating, again, has no effect on this. Use a stabilizer if the boat will be sitting.

(Message edited by chpthril on December 11, 2009)
Old     (05mobiuslsv)      Join Date: Apr 2006       12-11-2009, 8:35 AM Reply   
^^^^Wow Mike you know it all don't you.... Since you know all about gas can you tell me what else you will find in Regular Unleaded and Mid grade?

I'll answer for you since you probably don't know.

(Message edited by 05mobiuslsv on December 11, 2009)
Old     (psudy)      Join Date: Dec 2003       12-11-2009, 8:49 AM Reply   
Thanks Mike,
Is it better to run lower octane than higher, if the specific octane isn't available?
Old     (cwkoch)      Join Date: Aug 2006       12-11-2009, 9:14 AM Reply   
The minimum octane rating is the MINIMUM the engine was designed to run on. You're better off going higher, but most modern engines can compensate for lower octanes by retarding the timing.

As far as old or bad gas, that's a whole different can of worms..... Who knows what's in the station's tanks.
Old     (rallyart)      Join Date: Nov 2006       12-11-2009, 9:16 AM Reply   
Paul, running with an Octane rating too high won't damage anything, it just costs more. Running with rating too low can damage things, costing a lot more. It's better to run too high than too low.
That said, modern car engines can handle octane that is too low within their engine management programming is it is not severely too low. You are unlikely to damage a sophisticated engine from the last 10 years by running one grade lower fuel. You do run a risk by doing so though. Particularly at full throttle.
Old     (rallyart)      Join Date: Nov 2006       12-11-2009, 9:17 AM Reply   
Darn, Charlie has faster typing than me.
Old     (05mobiuslsv)      Join Date: Apr 2006       12-11-2009, 9:45 AM Reply   
Didn't see you answer Mike so here you go. Premium is cleaner because it doesn't contain some ingredients Regular and Mid-Grade do (since it is a blend of Premium and Regular). You will find a small ammount of diesel fuel or jet fuel in regular gasoline due to the way it's shipped. If a refinery has a load rack where they load transport trucks this won't be an issue since each product is piped directly to the storage tanks supplying the load rack. These trucks will only supply stations close to the refineries. The majority of refined petroleum products are shipped via pipelines and due to batch changes (product change) this is where there is a small ammount of contamination takes place. Is it an issue for an engine, No. All these products are still quality tested before they are shipped to gas stations. This is not the case with Premium, it's held to higher quality standards and the contamination does not take place which is where my "Clean" comment came from. The contamination is removed before the metering begins for the Premium product.

Only pipelines that don't ship multiple products won't have this small ammount of contamination in regular unleaded, and there are few of them.

By the way I would only buy gasoline where they move alot of product and that's not usually a ma a pa station.

Yes the EPA requires a very small ammount of cleaning additive, large gasoline producers add much more than is what's required. This is what's know as Top Teir gasoline.

"Trust me it's all smoke and mirrors".
Old     (chpthril)      Join Date: Oct 2007       12-11-2009, 3:53 PM Reply   
Nice copy'n paste there, Nubu. You would argue with a fence post if it told you the sky was blue and the sun was yellow

There you have it, "the great and powerful OzBu has spoken" so you all go out and by "Premium" priced gasoline
Old     (05mobiuslsv)      Join Date: Apr 2006       12-11-2009, 4:22 PM Reply   
Bite me mike that was no copy and paste I work in the industry D-bag.

Don't get pissed and try and blast me because you don't know what the F you're talking about.

(Message edited by 05mobiuslsv on December 11, 2009)
Old     (chpthril)      Join Date: Oct 2007       12-11-2009, 5:00 PM Reply   
"Bite me mike that was no copy and paste I work in the industry D-bag.

Don't get pissed and try and blast me because you don't know what the F you're talking about.

^^^ WOW, and you say i'm the pissed one? I'm having a blast getting you worked up to a point of posting like this.

Oh, not sure what "industry" you are in, maybe the Tonka industry cause your post makes you look about 5 yrs old, But i have 18 years in the automotive repair industry as a technician, service manager and instructor. I have attended training seminars held by engineers from GM, Ford, Chrysler, Toyota, VW, Porsche, Audi, Snap-On, and others. ASE Certified Master Technician, GM Certified, and Chrysler certified. So, if you want to play "whip out ur @%#$ and see who's is longer, i'm in!

Other wise, back off, chill out, and realize that others may know what they are talking about and may be correct, even though your opinion differs from theirs.
Old     (05mobiuslsv)      Join Date: Apr 2006       12-11-2009, 5:28 PM Reply   
Oil and gas industry Mike Refining and Marketing to be exact. Let's clarify something here Mike, never said you were wrong about anything you posted from your google search and paste, it was the other way around remember. Your "smoke and mirrors" theory . You said I was wrong about Premium unleaded being cleaner gasoline because you assumed I was talking about Octane levels. What I posted had nothing to do with octane levels and explained why it was a cleaner form of gasoline.

Thanks for the invite Mike but I have no desire to see your junk, don't swing that way but obviously you're not against it. Maybe you could actually utilize that thing this weekend, sounds like it's been a while.

I think you're still a little pissed about the ballast hose thread .
Old     (amo)      Join Date: Jan 2009       12-11-2009, 6:58 PM Reply   
This is awesome!!! Dudes from both sides of the issue.

Old     (chpthril)      Join Date: Oct 2007       12-11-2009, 7:29 PM Reply   
Well, if your post had nothing to do with octane levels, then you my friend, are in the wrong thread.

I should have guessed, you're in "Marketing" for the oil companies. Your X-mass bonus must hinge on you making consumers believe all that propaganda BS about Premium being better then regular. In other words, if you work in the oil biz, then you make a living off the oil company's profit, then your opinion is biased and there for is null.

Nope, the ballast hose thread just proves my point, you'd argue with a brick wall.

Well, I suppose you can dream up whatever definition you want for "clean" in order to make you right me wrong, but i stand behind my statement because it comes from engineers that build engines and fuel systems and not people that profit from selling over-priced gasoline like those in the "Oil Refinery and Marketing" depts.

"Maybe you could actually utilize that thing this weekend,"

Already have, your old lady is on her way home now

OK, that was over the top, but you did call me a D-bag
Old     (05mobiuslsv)      Join Date: Apr 2006       12-11-2009, 7:51 PM Reply   
Wow Mike you're about as dense as they come. Have a great weekend.

I think I'll take what I've learned from the industry, petroleum engineers, and working for a "super major" oil company (you can google that one to Mike) over a post from a retired, fired, or washed up "mechanic", or whatever you call yourself, any day of the week.

I sure wish I could enhance my bonus by posting on wakeworld. Unlike the boat sales world it doesn't work like that in my world.
Old     (zad0030)      Join Date: Jun 2007       12-11-2009, 8:09 PM Reply   
"I sure wish I could enhance my bonus by posting on wakeworld. Unlike the boat sales world it doesn't work like that in my world."

Obviously you think it enhances your ego.

(Message edited by zad0030 on December 11, 2009)
Old     (05mobiuslsv)      Join Date: Apr 2006       12-11-2009, 8:19 PM Reply   
Go to bed John D.
Old     (cla10beck)      Join Date: Dec 2007       12-12-2009, 8:24 PM Reply   
To answer the original question, I have the indmar carburated 350, and the manual calls for 89, but I run 87 and have not an pre-detonation issues. A carbed motor would have a harder time adjusting to lower octane because the spark advance is only done by vacuum, not by the computer like an EFI. My opinion is that 87 will work most of the time in our engines, they just state 89 because in some areas, it will be needed (high ambient temps and pressures)

As far as the difference between 87 and 91. I did a quick internet search and found the specs for each. I could not find any difference except for the research and motor octane numbers for each.

87 Octane -

91 Octane -

And I did sleep at a Holiday Inn Express last night
Old     (sanger)      Join Date: May 2002       12-13-2009, 3:51 PM Reply   
For what it's worth (not much) when I called Indmar a couple of years ago the bottom line was?

If you're going to use the fuel within 2 weeks 87 was fine otherwise go with 89. His reason was the degrading of fuel quality while it sits.

I know this will be bashed but that's what he said.
Old     (dru1974)      Join Date: Nov 2009       12-13-2009, 4:19 PM Reply   
Is that what you use Gary, Do you have the 325 hp indmar? any problems?
Old     (sanger)      Join Date: May 2002       12-13-2009, 4:45 PM Reply   
310 HP and never a problem. When I first got this boat I would listen very carefully for any pre-ignition under acceleration and it's always quite and smooth. Oct. thru May I add fuel stabilizer. My previous inboads had Mercs with 87 listed in the manual so I didn't really worry about it. If you consider which gas has the highest turnover at your local station I think it would be 87, how long does it take to use up 89 and 91?

The cost difference per fill up is small, use what makes you sleep better at night :-)
Old     (cadunkle)      Join Date: Jul 2009       12-14-2009, 9:28 AM Reply   
No reason to run low octane. Higher compression and more advanced ignition timing require higher octane to prevetn predetonation. Detonation will shatter pistons, crack rings and lands, weaken the tension in rings, cause ring flutter, stresses connecting rods, hammers and more bad things as well. Cheap out and it'll cost you in repairs in the long run.

Now if you either tune the engine for lower octane by recurving your distributor, or if a newer engine the knock sensor retards the timing, you likely won't have much chance of doing damage. The downside is you will be running a less than optimal timing curve which will result in increased fuel consumption, negating your $4 savings on filling that 40 gallon tank.

Here is what predetonation does to pistons, if you're fortunate enough to not have a catastrophic failure.
Old     (cla10beck)      Join Date: Dec 2007       12-14-2009, 11:12 AM Reply   
I think about like this. Indmar recommends 89 octane for most of its engines, no matter where the boat is being run. When the engine predetonates, the temperature and pressure combination in the cylinder is too high so the fuel ignites before the spark. So, the ambient temp and pressure are going to have a great affect on whether the gasoline ignites early.

This is the same reason you see 85 octane gasoline offered in colorado as regular because the starting pressure is lower, they don't have to worry about pre-ignition with 85. This is the same reason I can use 87 Octane with no hint of pre-detonation and normal spark timing.

Now, If I lived in Houston with the high temps at sea level, I would probably use 89 Octane
Old     (dru1974)      Join Date: Nov 2009       12-15-2009, 10:05 AM Reply   
Thanx for all the help guys, its an easy decision, Ill just burn the 89 and sleep soundly.


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